FIRE, Financial Independence, Retire Early, started as a fringe movement in the US. Today, it's a global framework for answering one question: how much money do I need before work becomes optional?
Key Insights
Savings rate is everything. Going from 10% to 50% savings rate cuts working years from 51 to 17.
4% rule assumes 7% nominal returns, 3% inflation, 30-year retirement with 95% success rate.
Three FIRE levels exist: Lean ($500K), Regular ($750K to $1M), and Fat ($1.5M+).
Sequence-of-returns risk is the biggest threat to early retirees: a bear market in year one can derail the plan.
Key Metrics
| Metric | Value | Context |
|---|---|---|
| Withdrawal rate | 4% | Trinity Study baseline |
| FIRE multiplier | 25x expenses | Based on 4% rule |
| Lean FIRE target | $500,000 | Under $20K/yr spending |
| Regular FIRE target | $750K to $1M | $30K to $40K/yr spending |
| Fat FIRE target | $1.5M+ | $60K+/yr spending |
| 50% savings rate | 17 years to FIRE | At 5% real return |
| 75% savings rate | 7 years to FIRE | At 5% real return |
The 4% rule (and its limitations)
The backbone of FIRE is the 4% rule, derived from the Trinity Study. If you withdraw 4% of your portfolio in year one of retirement, then adjust that amount for inflation each year, your portfolio has a ~95% chance of lasting 30 years with a stock/bond mix.
This means your FIRE number is simple: annual expenses x 25. If you spend $30,000/year, you need $750,000. Spend $20,000/year? $500,000.
$30,000/year spending = FIRE number: $750,000
$40,000/year spending = FIRE number: $1,000,000
$60,000/year spending = FIRE number: $1,500,000
The lower your expenses, the faster you get there. This is why FIRE enthusiasts often focus on reducing spending rather than increasing income.
The savings rate shortcut
Here's the elegant part: your savings rate alone determines how long you need to work, assuming a 5% real return. The math was popularized by Mr. Money Mustache:
| Savings rate | Years to FIRE |
|---|---|
| 10% | 51 years |
| 25% | 32 years |
| 50% | 17 years |
| 65% | 10 years |
| 75% | 7 years |
Going from 10% to 50% savings rate cuts your working years from 51 to 17. That's 34 extra years of freedom. And it's not about earning more — it's about spending less relative to what you earn.
Real-world example: $3,000/month net income
Let's take a concrete example. You earn $3,000/month after tax in the US. Here's how different savings rates play out:
| Savings/mo | Savings rate | Annual expenses | FIRE target | Years to FIRE |
|---|---|---|---|---|
| $300 | 10% | $32,400 | $810,000 | ~51 years |
| $750 | 25% | $27,000 | $675,000 | ~32 years |
| $1,500 | 50% | $18,000 | $450,000 | ~17 years |
| $2,250 | 75% | $9,000 | $225,000 | ~7 years |
The double benefit: higher savings rate means you invest more and need a smaller FIRE number (because you're used to spending less). It compounds in both directions.
Three types of FIRE
Lean FIRE: Annual expenses under $20,000. FIRE number around $500,000. Requires significant lifestyle optimization but achievable relatively quickly.
Regular FIRE: $30,000 to $40,000/year expenses. FIRE number $750,000 to $1,000,000. The most common target for dual-income households in the US.
Fat FIRE: $60,000+/year expenses. FIRE number $1.5M+. Requires high income or extreme patience, but gives a more comfortable post-work life.
Common FIRE mistakes
Ignoring healthcare costs. In the US, healthcare is often the biggest post-retirement expense. Budget $5,000 to $10,000/year even with ACA subsidies.
Assuming fixed returns. The 4% rule assumes a 7% nominal return. Sequence-of-returns risk can derail early retirees who hit a bear market in their first years. Consider a more conservative 3.5% withdrawal rate.
Forgetting inflation. Your FIRE number needs to grow with inflation. A $750,000 target today needs to be higher if you're 20 years from retirement.
Use the FIRE calculator to find your exact retirement date based on your income, savings rate, and expected returns. It factors in inflation and shows you exactly how many years stand between you and financial freedom.